36 THE FLIGHT OF BIRDS 



a skilled and experienced pilot, he is, apparently, 

 as steady as he rushes down towards the earth as 

 a bird could be. But, if he did lose his balance, it 

 would be fatal, whereas to the bird a momentary 

 loss of equilibrium is of no consequence. 



Leaving aviators and their splendid achievements, 

 I must describe another attitude sometimes adopted 

 by a bird in gliding downward. He will extend his 

 wings to the full, but hold them slanting upward 

 (see PI. in). Obviously in this position the wings 

 give less support, and so he descends. But he 

 descends slowly, not with the rush that is character- 

 istic of the head-foremost downward glide. The 

 wings do not travel edgeways through the air and 

 so they check his pace. Their upward slant is, as 

 I have before remarked, advantageous to balance. 



I must now conclude this brief investigation of 

 the bird's stability when on the wing. What we 

 see in the flight of birds — I am not now speaking 

 of soaring — is not a steady, careful maintenance 

 of equilibrium, but an instantaneous recovery of 

 balance whenever it is lost. The bird can afford 

 to be indifferent to the difficult problems which 

 this subject presents. He has something much 

 better than the power of maintaining equilibrium. 

 However the gusts and vagaries of the wind may 

 upset him, he can right himself at once. He owes 

 his wonderful stability to some extent to his fine 

 build and the elasticity of his feathers, but mainly 

 to manoeuvres and adjustments that cannot be 

 mere reflexes. The flying machine which he pilots 

 is admirably built : still it can never dispense with 

 a pilot. But his voluntary adjustments are largely 



